(1) Field of the Invention
The invention relates to electrically powered vehicles and is directed more particularly to a self-propelled electrically driven wheel for such vehicles.
(2) Description of the Prior Art
In response to environmental and geopolitical problems, it has become of some urgency to make available a vehicle consuming relatively less fossil fuel than current fossil-fuel vehicles. While the ultimate target remains "zero-emissions" vehicles which utilize virtually no fossil fuel, realization of that goal appears far removed because of lack of progress in development of batteries capable of propelling a vehicle for times and distances, and at speeds, the driving public has come to expect.
It is now believed that in the interim hybrid vehicles utilizing a combination of a fossil-fueled engine and electric drive means may well be the answer, falling short of "zero-emissions", but nevertheless greatly increasing the distance one can travel on a gallon of fossil fuel. One such concept includes providing an electric motor for each wheel, the motors being driven by a generator which, in turn, is driven by a fossil-fuel engine. In such instance, the engine can be run solely for benefit of the generator and therefore can be small and run at a constant most efficient speed, greatly reducing fossil fuel requirements. To reduce the fossil fuel requirements further, it is necessary that the wheel motors be as efficient as possible.
Two types of rotary electrical motors have been considered, the axial permanent magnet motor and the radial permanent magnet motor. While there are numerous embodiments of both types, in general the axial permanent magnet motors feature a stator disk, or drum, with a central opening and electrical conductor windings wound through the central opening and across the outer peripheral edge of the stator disk. The stator disk typically is fixed in place. A rotor usually is mounted on a shaft and is proximate to the stator disk. The rotor is provided with permanent magnets extending radially from the center of the rotor. In operation, a polyphase alternating electrical current passed through the windings of the stator disk creates a magnetic flux, to which the permanent magnets of the rotor respond, to cause turning of the rotor and the shaft to which the rotor is fixed. The portion of the windings overlying the outer peripheral edge of the stator disk do not accomplish useful work. The magnetic field generated by the windings on the outer peripheral edge of the stator is not coupled with any of the permanent magnets in the rotor and is therefore wasted.
In general, in radial permanent magnet motors, the stator is annularly-shaped and is concentrically disposed around a generally cylindrically-shaped rotor. The stator is provided with electrically conductive windings wound about and in between teeth which extend radially inwardly from the stator toward the rotor. Portions of the windings ("end-turn wire") extend around the outer periphery of the stator. The rotor is provided with permanent magnets of alternating polarity disposed around the periphery of the rotor. The permanent magnets of the rotor react to a magnetic field created by current through the stator windings, to cause the rotor to turn. The rotor generally is connected to a shaft which turns with the rotor and accomplishes work. In the radial motor, the end-turn wires of the stator are not useful in creating the magnetic field which couples with the rotor permanent magnets.
Thus, there is a need for an efficient motor-wheel for vehicles at least in part electrically powered, and there is a need for more efficient motor components for use in such a vehicle wheel.